Question

A ball thrown vertically upwards with speed 'u'from the top of a tower reaches the ground in 9 sec. Another ball thrown vertically downwards from the same position with speed 'u', takes 4 sec to reach ground. Calculate the value of 'u' . (g=10 ms^-2)

Answer 1

take 1st ball be b1 and another be b2.

ac/eq of motion

v=u+at

for b1

v=0(at highest height)

0=u-10×9(in case of of upward direction)

u=90m/sec

for b2, in this case final velocity is "u" since,

v=u + gt

=0+10×4

v=40m/sec

so,u1=90m/sec& u2=40m/sec

Answer 2

Answer:

25 ms is write answer it will help you